test-fenv: Don't test non-standard modes on BID
test-fenv: Don't test non-standard modes on BID

These are quite undefined when running on most hardware,
there should be no expectation they work or do anything.

BID coerces to one of the 5 IEEE dfp modes.

gftg85/libdfp,gftg85/libdfp,gftg85/libdfp,gftg85/libdfp